This invention relates to a packaging apparatus. More particularly, this invention relates to a method and apparatus for automatically forming a package from plastic packaging material, and sealing it to prevent the entry of oxygen and the like.
Prior art machines have certain known disadvantages. For example, in some packaging machines the product containers, typically tray-like package forms, are moved from station to station with an intermittent indexing motion, as in U.S. Pat. No. 3,061,984. Thus, all containers are alternately accelerated and decelerated, so that when such machines are used for liquid products, products containing large portions of non-viscous liquids or powdered products, the products tend to spill out of the container. Other machines, such as are shown in U.S. Pat. No. 2,935,828, employ a rotary drum which also introduces spillage problems. The present invention overcomes these disadvantages by moving the product container through the machine in an upright position in a horizontal plane and at substantially constant speeds, while the packaging operations are being performed.
U.S. Pat. No. 3,540,186 discloses a continuous movement machine which, however, fails to solve certain problems of considerable commercial importance. For instance that machine is incapable of forming the package parts and requires pre-manufactured containers for its packaging operation. Further, the construction of the support means for the tray carriers is such that the forces generated within the packaging mechanism are transmitted into the supporting structure which thereby necessitates the use of a generally heavier and more costly construction. An additional disadvantage is that the use of carriers with defined interior contours limits the shape of the packaging profiles which can be produced and/or used with the machine. Further in that regard, when it is desired to change the package profile, it is necessary to change or modify all of the tray carriers (sometimes numbering in the hundreds).